The NW7US Beacon

Here is this week’s space weather and geophysical report, issued 2015 Apr 27 0348 UTC.

Highlights of Solar and Geomagnetic Activity 20 - 26 April 2015

Solar activity was at low to high levels throughout the period. Region 2322 (N11, L=116, class/area=Dac/60 on 21 April) grew and intensified as it rotated to the western limb; producing numerous low level C-class flares and five moderate level M-class flares on 21 April. Region 2322 also produced the largest flare of the period, an impulsive M4/Sf at 22/1545 UTC. Region 2322 continued to produce C-class and M-class flares until it rotated beyond the western limb by 24 April, including a long-duration M1 flare at 23/1007 UTC with an associated Type-II radio sweep and coronal mass ejection (CME) from the western limb as observed in SOHO/LASCO C2 imagery. The CME was not Earth-directed.

Regions 2325 (N05, L=050, class/area=Cai/220 on 19 April) and 2326 (N20, L=086, class/area=Cao/80 on 23 April) were the other most prolific flare producers during the period. Region 2325 produced an M1 flare at 21/2201 UTC and Region 2326 produced numerous C-class X-ray flares with the most notable being a C7 flare at 23/1203 UTC. Both flares were very impulsive and did not have any observed optical flares nor notable radio signatures.

No proton events were observed at geosynchronous orbit.

The greater than 2 MeV electron flux at geosynchronous orbit was at moderate to high levels during the week; reaching high levels on 20-21 April and 24 April with a peak flux of 2,620 pfu on 20 April.

Geomagnetic field activity was at quiet to unsettled levels on 20 April as Earth was in a background ambient solar wind environment. On 21 April, Earth came under the influence of an isolated positive coronal hole high speed stream (CH HSS) and solar wind speeds increased to over 600 km/s as measured at the ACE satellite. This CH HSS produced occasional periods of active levels of geomagnetic activity from 21-24 April. The CH HSS rotated out of a geo-effective alignment by midday on 24 April and the winds decreased to mainly nominal solar wind conditions of about 375 km/s, returning Earth to quiet to unsettled geomagnetic conditions.

During the week, ACE solar wind parameters measured a high wind speed of 628 km/s on 21/0632 UTC and a low wind speed of 291 km/s on 26/1123 UTC. Total field (Bt) ranged from about 1 to 14 nT, while the Bz component varied between +12 to -7 nT. The phi angle was generally in a positive (away from the Sun) orientation with a short period of negative (towards the Sun) sector to begin the week.

Forecast of Solar and Geomagnetic Activity 27 April - 23 May 2015

Solar activity is expected to be at very low to low levels through 03 May due to the low number of complex active regions. Solar activity levels are expected to increase to low levels; with a slight chance for moderate (R1-R2/minor-moderate) levels beginning 04 May with the return of Region 2322 (N11, L=116) and remain at low levels, but increase to a chance for moderate (R1-R2/minor-moderate) levels beginning 07 May as Region 2326 (N20, L=086) also rotates back onto the disc. Solar activity level is expected to decrease back to very low to low levels with the departure of Regions 2322 and 2326 beginning 17 May.

No proton events are expected at geosynchronous orbit.

The greater than 2 MeV electron flux at geosynchronous orbit is expected to be at normal to moderate levels from 27 April-06 May, normal levels from 07-12 May, moderate to high levels from 13-14 May, high levels from 15-18 May, moderate levels from 19-20 May, and moderate to high levels from 21-23 May.

Geomagnetic field activity is expected to be at quiet levels from 27-28 April and increase to quiet to unsettled levels beginning 29 April due to CH HSS effects. Field activity is expected to begin decreasing by 02 May, with overall quiet levels likely from 03-10 May. Field activity is expected to increase to unsettled to active levels beginning late on 11 May and likely reaching active levels on 12-13 May due to CH HSS effects. Field activity is expected to decrease to unsettled to active levels by 14 May as CH HSS effects begin to wane; and return to quiet to unsettled conditions from 15-17 May. Field conditions are expected to increase to unsettled to active levels on 18 May due to a CH HSS and return to quiet to unsettled conditions as the CH HSS rotates out of a geo-effective position by 21 May, and remain at quiet levels for the remainder of the outlook period.

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